1. Field of the Invention
This invention relates to chemical processes carried on especially in deeply-packed beds of inert carrier material which bear reactants, exposing them to a contaminated fluid stream, for example. For sweetening streams of natural gas polluted with hydrogen sulfide, such beds of carrier material may typically be ten feet or more in depth, and must not crush under its overlaying weight.
2. Description of the Related Art
U.S. Pat. No. 5,320,992, dated May 28, 1993, discloses that calcined montmorillonite serves as an inert mineral carrier for reactant oxides used in sweetening natural gas polluted with hydrogen sulfide. It is strong enough that the packed beds may be as deep as 20 feet without compacting. To achieve such strength and to attach reactant oxide particles as well, it is calcined. Porosity obtained by calcining serves to absorb and retain water sufficiently that, after draining, when the moist particles are intermixed with a reactant iron oxide, the oxide will be retained on the particles to react hydrogen sulfide which pollutes the natural gas.
Shale and slate are the principal clay minerals which, when heated beyond calcining temperature, bubble within and expand ("bloat"); (Society of Mining Engineers "Industrial Minerals and Rocks" [1983], p. 82). They do not lose their strength when bloated, and are used to serve as light-weight aggregates for concrete.
Expanded perlite, which is not strong enough for such use, is shown in U.S. Pat. No. 4,201,751 to Holter, to be sprayed, along with water and caustic soda, to purify very hot gases (at temperatures up to 750.degree. C.) in a turbulent gas stream.